Cascade connected transformer

ABSTRACT

A cascade connection transformer having main primary and secondary windings closely coupled to each other, an auxiliary primary winding having the same number of turns as the main primary winding and connected in parallel therewith, and a tertiary winding closely coupled with the auxiliary primary winding.

United States Patent [72] Inventors Tellchl Sllumoto; [50] Field of Search 336/180, Jun Nlehldll, both of Kyoto, Japan 206, I70, 171, l84, 182; 323/48, 49, 6 [2| Appl. No. 29,739 1221 Filed Apr. 24, 1970 1 Refmnm C 45] Patented Oct. 5, l97l UNITED STATES PATENTS l a Nil-In Electric m! Llmmd 1,706,193 3/1929 Stephens 336/170 y JIPIII 3,196,345 7/1965 Dobsa 336/l 70 X Pmmy 26, 1967 3,395,335 7/1968 Storey 323/48 ux 1pm [3 l 1 42/6892! FOREIGN lAjI'ENTS Continuation of application Sen 574,778 1946 Great Br1ta1n 323/48 758,910, Sept. 10, 1968, now abandoned. Primary Examiner--Thomas J. Kozma 54] CASCADE CONNECTED TRANSFORMER AllSTRACT: A cascade connection transformer having main pnmary and secondary wmdlngs closely coupled to each 3 Clauns, 4 Drawing Figs.

other, an auxiliary primary wlndmg havmg the same number [52] {1.5. CI 336/170, of turns as the main primary winding and connected in parallel 323/48, 336/180, 336/ l 84 therewith, and a tertiary winding closely coupled with the aux- [5 l Int. Cl H0" 2 7/26 iliary primary winding.

4/ l l 9 --l2 PATENIED nm 5 nm FIG. I

PRIOR ART FIG. 4

FIG. 2

INVENTORS.

TEHCHI SAKAMOTO JUN NISHIDAI MWM% W ATTORNEYS,

CASCADE CONNECTED TRANSFORMER This application is a continuation of application Ser. No. 758,910 filed Sept. 10, I968, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to cascade connected transformers.

2. Description of the Prior Art Cascade connected transformers conventionally contain a plurality of transformer units in which a primary winding, a secondary winding and a tertiary winding for exciting a transformer unit of the next stage are concentrically wound around an iron core. This results in the nonunifonnity of the length in the axial direction between the primary winding and the secondary winding or between the primary winding and the tertiary winding. As a result, the coupling is extremely inferior because of a great deal of flux leakage as a result of the nonuniforrnity. This flux leakage has customarily been prevented by circulating current generated by a connecting winding in parallel to the main winding. However, this method produces a large, bulky device which is expensive because the connecting winding does not contribute directly to the output volt-amperes of the transformer.

SUMMARY OF THE INVENTION The device of the present invention includes a main primary winding coupled closely to a secondary winding and an auxiliary primary winding coupled closely to a tertiary winding in parallel with the main primary winding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of the prior art devices;

FIG. 2 is a schematic view of one embodiment of the present invention;

FIG. 3 is a schematic view of another embodiment of the present invention; and

FIG. 4 is a schematic view of the embodiment shown in FIG. 3 wherein the cascading effect has been shown.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 wherein the conventional transformer for cascade connection is shown, a primary winding 1, a secondary winding 2 and a tertiary winding 3 for exciting a transformer unit of the next stage are concentrically wound about an iron core 4. In order to prevent flux leakage due to the nonuniformity of the windings, connecting windings 5 have been provided to circulate current.

The need for connecting windings 6 and 7 of FIG. I has been eliminated in the improvement shown in FIG. 2. A main primary winding 8 is closely coupled to a secondary winding 2. An auxiliary primary winding 9 is connected in parallel with main primary winding 8 and is coupled closely to a tertiary winding 3 which carries out the cascade connection of a plurality of transformer units. The number of turns of main primary winding 8 and auxiliary primary winding 9 are equal. A layer of insulation 10 is provided between a low-potential part comprising an iron core 4 and both primary windings 8 and 9 and a high-potential part including secondary winding 2 and tertiary winding 3. Because the primary windings are of the same number of turns, a circulating current does not occur when there is no load. Since the coupling between main primary winding 8 and tertiary winding 3 and between auxiliary primary winding 9 and secondary winding 2 is extremely loose in comparison with the coupling between main primary winding 8 and secondary winding 2 and between auxiliary primary winding 9 and tertiary winding 3, the output of secondary winding 2 and tertiary winding 3 are respectively supplied through main primary winding 8 and auxiliary primary winding 9. Therefore, leakage flux does not increase under load.

Assuming the volt-amperes of the secondary winding is represented by P and that of the tertiary winding is represented by P com arin the sums of volt-amperes of respective windings in GS. and 2, the fonner needs voltamperes of 2P +3P- while the latter needs only volt-amperes of 2P,+2P

Referring to FIGS. 3 and 4, a plurality of transformer units connected in cascade relationship are shown whereas a secondary winding 2 and a main primary winding 8 are coupled closely to and wound about a main path 11 of an iron core 4 having a return path 12. A tertiary winding 3 and an auxiliary primary winding 9 are also coupled closely to iron core 4 about the return path 12. Because the mutually tight-coupled windings are respectfully wound about a main path and a return path of the iron core, as compared with the case which all windings are wound about the same magnetic leg, it is possible to decrease the diameter of the windings, to lighten the weight of the apparatus and to make the coupling between the windings superior. Further, it is convenient to use the gap formed between the main path and the return path of the iron core effectively with respect to insulation.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

We claim:

1. A plurality of cascade connected transformers, each of said transformers comprising;

a main primary winding,

a secondary winding inductively coupled to said main primary winding,

an auxiliary primary winding having the same number of turns as said main primary winding,

means connecting said auxiliary primary winding in parallel with said main primary winding,

a tertiary winding inductively coupled to said auxiliary primary winding,

an iron core carrying said main and auxiliary primary windings, said secondary winding and said tertiary windmg,

an insulating layer positioned between said main and auxiliary windings and said secondary and tertiary windings for isolating said secondary and tertiary windings from said main and auxiliary primary windings and said iron core, and

- means electrically connecting the tertiary winding of each of said plurality of transformers across the main and auxiliary primary windings of another one of said plurality of transformers.

2. A plurality of cascade connected transformers as defined in claim 1 further including,

means serially connecting each of said secondary windings to its corresponding tertiary winding, a secondary winding and its corresponding tertiary winding being wound on the same one of said plurality of transformers.

3. A plurality of cascade connected transformers as defined in claim 2 wherein each of said plurality of cascade connected transformers further comprises,

an iron core having a main path and a return path and wherein said main primary winding and said secondary winding of each of said plurality of transformers are wound around said main path of their corresponding iron core and said auxiliary primary winding and said tertiary winding of each of said plurality of transformers are wound about said return path of their corresponding iron core. 

1. A plurality of cascade connected transformers, each of said transformers comprising; a main primary winding, a secondary winding inductively coupled to said main primary winding, an auxiliary primary winding having the same number of turns as said main primary winding, means connecting said auxiliary primary winding in parallel with said main primary winding, a tertiary winding inductively coupled to said auxiliary primary winding, an iron core carrying said main and auxiliary primary windings, said secondary winding and said tertiary winding, an insulating layer positioned between said main and auxiliary windings and said secondary and tertiary windings for isolating said secondary and tertiary windings from said main and auxiliary primary windings and said iron core, and means electrically connecting the tertiary winding of each of said plurality of transformers across the main and auxiliary primary windings of another one of said plurality of transformers.
 2. A plurality of cascade connected transformers as defined in claim 1 further including, means serially connecting each of said secondary windings to its corresponding tertiary winding, a secondary winding and its corresponding tertiary winding being wound on the same one of said plurality of transformers.
 3. A plurality of cascade connected transformers as defined in claim 2 wherein each of said plurality of cascade connected transformers further comprises, an iron core having a main path and a return path and wherein said main primary winding and said secondary winding of each of said plurality of transformers are wound around said main path of their corresponding iron core and said auxiliary primary winding and said tertiary winding of each of said plurality of transformers are wound about said return path of their corresponding iron core. 